Drawing-board



(No Model.) 2 SheetS- Sheet 1.

A. H. JOHNSON.

DRAWING BOARD. I No. 495,157. PatentedApr. 11,1893.

(No Model.) 2 Sheets-Sheet; 2.

A.H. JOHNSON.

DRAWING BOARD, Patented-Apr. 11

s W 9 n. JD E UNITED STATES PATENT OFFICE.

ALBERT H. JOHNSON, OF TAMPA, FLORIDA.

DRAWING-BOARD.

SPECIFICATION forming part of Letters PatentNo. 495,157, dated April 11,1893.

Application filed July 21, 1892. Serial No. 440,823. (No model.)

To all whom it may concern.-

Be it known that I, ALBERT H. J OHNSON, a citizen of the United States,residing at Tampa, in the county of I-Iillsborough and State of Florida,have invented a new and useful Drawing-Board, of which the following isa specification.

My invention relates to drawing, and refers particularly to the boardsused therein, the object of my improvement being to produce a boardwhereon perspectives may be drawn, the horizontal vanishing points, andpoint of sight being determined by gages provided for that purpose.

To this end the invention consists in a board provided at opposite sideswith curves or curved guides, operated by slides mounted upon gages, forobtaining the horizontal vanishing points, and similar guides locatedbeneath the board and provided with a swinging arm to determine thepoint of sight.

My invention is described in detail in connection with the drawings,andthe novel features thereof are particularly pointed out in the appendedclaims.

In the drawings: Figure 1 is a perspective View of aboard embodying myimprovement, broken away to show the devices for determining the pointof sight. Fig. 2 is a plan view showing the boards provided withdrawings, and indicating by dotted lines the manner of using a T-squarethereon. Fig. 3 is a detail view of one of the curved guides with itsattached slide. Fig. 4 is a similar View of the swinging arm detached.

The frame of my improved board comprises the parallel side-bars AA,connected by the transverse strips B, the boards or drawing surfaces, 0O, being secured to said trans verse strips by retaining-screws D.

Projecting from opposite sides of the frame, are the gage-arms, E E,preferably formed by the projecting ends of a transverse bar F, saidarms being provided with scales to indicate the number of feet from thepoint of sight of the vanishing-points. Mounted upon these gage-arms areslides G, to which are connected the centers of the guides H, the slidesbeing provided in their upper sides with transverse grooves to receivethe lower edges of the guides, and the latter being secured in place byset-screws I. The slides are locked at the desired point of thegage-arms by thumbscrews K. The free ends of the guides engage verticalpins, which are carried by the lateral arms L, whereby the ends of theguides, which are of spring-metal, are held in place while the centersthereof are moved by means of the slides to produce the desiredcurvature. An ordinary T-square, placed within the curved guides withthe ends of the head of the former bearing against the concaved surfacesof said guides, will lie in the direction of the horizonalvanishing-points of the drawing, as indicated in Fig. 2, for the reasonthat the blade of the T-square is perpendicular to the cord which isdescribed by the head.

In projecting a perspective from a plan view, it is necessary, in orderto determine the correct proportions of the former, to establish a pointof sight at the desired distance from the supposed building or object,and to enable this point of sight to be established by scale in order toobviate the necessityof measurement to produce the desiredforeshortening 0f the perspective, I provide a construction similar tothat used for determining the horizontal vanishing-points, the sameconsisting of a curved guide M, the ends of which engage pins N, locatednear the side-bars of the frame, and the center of which is carried by aslide 0, similar to those above described, and mounted upon a gagearm,which is located centrally between and parallel with the side-bars.

A head 1?, provided at its ends with depending notched studs to engagethe upper edge of the curved guides, operates in connection with theguide M, and carries a blade Q, provided with a slot to operate on pinson the head, and further provided with an ofiset R, whereby the free endof the arm lies on the surface of the supplemental drawing board orsurface. Adjacent to the said offset, and on the plane of the drawingsurfaces, is arranged a pin S, with which is adapted to be engaged theeye or perforation T, which is usually found in the end of the blade ofan ordinary T-square.

The devices for obtaining the point of sight are located below the planeof the drawing surfaces, and the free end of the swinging arm projectsfrom the perspective, its free end lying upon the plan view from whichthe perspective is projected, as shown in Fig. 2. With the eye orperforation of the T-square engaged with the vertical pin at the offsetof the swinging arm, and the inner side of the head of said T-squareoperating in contact with the opposite edge of the drawing surface uponwhich the perspective is to be drawn, it will be seen that by moving theT- square laterally of the drawing, the free end of the swinging arm iscaused to describe an arc, while the vertical pin is held by the T-square at a uniform distance from the near edge of the drawing surface.Thus, the point X, on the plan View, as shown in Fig. 2, when projectedby means of the device as described, is projected upon the point X ofthe perspective, the lines of projection being indicated in dotted linesin said figure. It will be seen that all lines of projection from theplan to the perspective, converge toward the assumed point of sight, Y,at the center of the perspective.

It will be understood that the graduations upon the gage-arm arearranged with respect to a certain scale upon which the drawings are tobe made, and the curve described by the guide is a segment of a circleof which the particular graduation indicates the length of the radius.

Having thus described my invention, what I claim, and desire to secureby Letters Patent, is-- 1. In a drawing apparatus, the combination witha drawing-board, of a curved guide located thereunder, a swinging armcarried by said guide so as to lie at all times in the direction of theradius of the circle of which the guide forms 'an are, one part of saidarm projecting beyond the edge of the board, and a T- square pivotallyconnected to the projecting portion of the arm, substantially asspecified.

2. A drawing-board, having an adjustable curved guide, a head providedwith notched studs to slide on said guide, and a swinging arm carried bysaid head and held at all times in the direction of the radius of thecircle of which said guide is an arc, in combination with a T -squareconnected to said swinging arm, substantially as specified.

3. A drawing-board, having a curved guide, a head to slide on saidguide, and a swinging arm attached to and longitudinally movable uponsaid head,in combination with a T-square connected to the swinging arm,substantially as specified.

4. A drawing-board, having a curved guide, a head slidably mountedthereon, and provided with guide-pins, and a slotted swinging arm havingits slot engaged by said pin and carrying a vertical pin at the plane ofthe drawing surfaces, in combination with a T- s'quare having its eye orperforation engaged with said Vertical pin, substantially as specified.

5. A drawing-board, having laterally-proj ecting gage-arms, and thespring-metal guides engaged at their free ends with stationary,

6. A drawing-board, having laterally-pro-* jecting guides, slidesmounted on said guides and provided with thumb-screws, and guidesattached at their centers to said slides and engaged at their free endsby stationary pins, substantially as specified.

7. A drawing-board, provided with lateral arms bearing pins and arrangedin pairs, the intermediate graduated arms bearing slides, and thespring-guides carried at their centers by said slides and engaged attheir ends by the said pins, substantially as specified.

8. In combination with a drawing-board, a swinging arm provided with apin at the plane of the upper surface of the board to engage the eye orperforation of a T- square, substantially as specified.

9. In combination with a drawing-board, a curved guide, means foradjusting the curvature of said guide, and a swinging arm provided witha head to slide on said guide, and having a T- square detachablyconnected thereto substantially as specified.

In testimony that I claim the foregoing as my own I have hereto affixedmy signature in the presence of two witnesses.

ALBERT H. JOHNSON.

Witnesses:

SAM. P. FRIERSON, AUSTIN C. ORDWAY.

